Thin-film solidification

Figure 1. Schematic of thin>film solidification system.

Figure 2. Photographs of cellular and dendritic structures in a thin-film solidification experiment of an organic alloy (succinonitrile-acetone) reported by Ref. 6.

The theory of seaweed formation does not only apply to solidification processes but in fact to the completely different phenomenon of a wettingdewetting transition. To be precise, this applies to the so-called partial wetting scenario, where a thin liquid film may coexist with a dry surface on the same substrate. These equations are equivalent to the one-sided model of diffusional growth with an effective diffusion coefficient which depends on the viscosity and on the thermodynamical properties of the thin film. 

Fig. 4 Schematic representation of control over block copolymer thin film orientation by directional eutectic solidification. The scheme shows control of polystyrene-b-polyethylene (PS-b-PE) block copolymer microdomain orientation through directional crystallization of benzoic acid (BA), (taken from [95])...

Yoon J, Lee W, Thomas EL (2006) Highly oriented thin-film microdomain patterns of ultra-high molecular weight block copolymers via directional solidification of a solvent. Adv Mater 18(20) 2691... 

Rapid solidification 10 -10 Pulsed laser melting of a solid surface Amorphous and nanocrystaUine thin films... 

As with solidification microstmctures, kinetic factors are as important as thermodynamics. For example, the (2 0 0) surface has the lowest energy in TiN. But the preferred orientation of TiN thin films can vary between (111) and (2 0 0), depending on deposition conditions. This means that the texture depends on kinetic factors as well as the energy minimization. 

The nature of thin films may also be influenced by rapid, thermally driven fluctuations in the local density of liquids. Heuberger, Zach and Spencer performed force and refractive index measurements of hexane confined to nanometer thickness using fast spectral correlation spectroscopy, and observed the fluctuations in density. This finding may help explain observations of high surface mobility, anomalously fast selfdiffusion, and apparent solidification in liquid films. 

There are five submethods in the test (ASTM D-611, IP 2) for the determination of the aniline point (1) Method A is used for transparent samples with an initial boiling point above room temperature and where the aniline point is below the bubble point and above the solidification point of the aniline-sample mixture (2) method B, a thin-film method, is suitable for samples too dark for testing by method A (3) methods C and D are used when there is the potential for sample vaporization at the aniline point (4) method D is particularly suitable where only small quantities of sample are available and (5) method E uses an automatic apparatus suitable for the range covered by methods A and B. 

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